New Ultrasonic Parking Sensor System in Automobiles

A highly accurate ultrasonic parking sensor system for use in air is described. The proposed system uses a method which combines both the time-of-flight (TOF) method and the phase-shift method. The proposed method can obtain larger range measurement and also get higher accuracy compared with the TOF method. A single-chip microcomputer-based two-frequency continuous signal generator and phase detector was designed to record and compute the TOF, two phase shifts, and the resulting distance. In the test embodiment to confirm concept feasibility, three cost 40±2kHz ultrasonic transducers allow flexibility on bumper for transmitting and receiving ultrasound. The ultrasound transducer on the middle of bumper is transmitting the ultrasound. Two ultrasound transducers on the left and right sides of bumper are receiving the ultrasound simultaneously for detecting multiple objects. Experiments were done in air using two-frequency continuous wave (TFcw) with the frequencies of 40 and 41kHz. Distance resolution of 0.05% of the wavelength corresponding to the frequency of 40kHz was obtained. The range accuracy was found to be within ±0.05mm at a range of over 3,000mm. The main advantages of this ultrasonic parking sensor system are high resolution for detecting multiple objects, low cost, narrow bandwidth requirements, and ease of implementation.